This document provides an overview of basic principles of antimicrobial therapy. It discusses key terms like antimicrobial, pharmacodynamics, pharmacokinetics and selective toxicity. It also covers topics like antibiotic resistance, restricted antibiotics, selection of antibiotics, antibiotic combinations, classification of antimicrobials by category and common drugs and their indications and adverse drug reactions. The document serves as a comprehensive reference on fundamental concepts in antimicrobial treatment and management.

1. Dr. Jibin Mathew, Pharm D.,
Clinical Pharmacology
BASIC PRINCIPLES OF
ANTIMICROBIALS

2. BASIC PRINCIPLES OF ANTIMICROBIAL THERAPY
• Antimicrobial - An antimicrobial is an agent that kills microorganisms or inhibits their growth.
• The primary difference between antibacterial and antimicrobial substances is the types of
microorganism they act upon. While antibacterial products prevent the development of bacteria,
antimicrobial agents such as alcohol-based hand sanitizers prevent the spread of bacteria, fungi,
and some viruses.
• Pharmacodynamics is how the drugs acts on the body. The mode of action of the drug is the
action at the cellular or molecular level. The therapeutic action is the end result of the drug action
• Pharmacokinetics is the way the body acts on the drug once it is administered. It is the measure
of the rate (kinetics) of absorption, distribution, metabolism and excretion (ADME).
• Selective toxicity = the ability of a drug to injure a target cell or organism without injuring other
cells or organisms that are in intimate contact .

3. ANTIBIOTIC RESISTANCE
Antibiotic resistance occurs when bacteria change in some way that reduces or eliminates the
effectiveness of drugs, chemicals, or other agents designed to cure or prevent infections. The bacteria
survive and continue to multiply causing more harm. Bacteria can do this through several mechanisms.
 The prescriber should closely adhere to the five rights of drug administration: the right patient, the
right drug, the right dose, the right route, and the right time.
 Narrow-spectrum antibiotics are preferred over broad-spectrum antibiotics when possible, as
effectively and accurately targeting specific organisms is less likely to cause resistance
Reasons for the widespread use of antibiotics include:
• increasing global availability over time since the 1950s
• uncontrolled sale in many low or middle income countries, where they can be obtained over the
counter without a prescription, potentially resulting in antibiotics being used when not indicated.
This may result in emergence of resistance in any remaining bacteria.
Supra infection (or super infection) : A new infection that appears through the course of treatment for
a primary infection

4. RESTRICTED ANTIBIOTICS
LIST OF RESTRICTED ANTIBIOTICS:
1) COLISTIN
2) TIGECYCLINE
3) LINEZOLID
4) VANCOMYCIN
5) CASPOFUNGIN
6) AMPHOTERICIN
7) DORIPENEM
8) IMIPENEM
9) MICAFUNGIN
10) MEROPENEM

5. SELECTION OF ANTIBIOTICS
Factors to take into consideration:
 The identity of the infecting organism.
 Drug sensitivity of the infecting organism
 Host factors (i.e. site of the infection, status of host defenses).
 Empiric therapy prior to completion of lab tests
 It may be necessary to begin treatment in patients with serious infections BEFORE the lab results.
 Age (infants and elderly highly vulnerable to drug toxicity).
 Pregnancy and lactation
 Previous allergic reactions
 Genetic factors (i.e. hemolysis in patients with G-6PD deficiency if given sulfonamides).
IMPERATIVE : Patients should be instructed to take their medication for the entire prescribed course
even though symptoms may subside before the full course has been completed.

7. ANTIBIOTIC COMBINATIONS
The result may be additive, potentiate or antagonistic.
• Additive response : one in which the antimicrobial effect of the combination is equal to the sum of
the effects of the two drugs alone.
• Potentiate interaction : one in which the effect of the combination is GREATER than the sum of the
effects of the individual agents
• Antagonistic response : in certain cases the combination of two antibiotics may be less effective
than one of the agents by itself (i.e. combination of a bacteriostatic with a bactericidal
• drug)
Disadvantages of antibiotic combinations:
 Increased risk of toxic and allergic reactions
 Possible antagonism of antimicrobial effects.
 Increased risk of Suprainfection
 Selection of drug resistant bacteria.
 Increased cost.

8. CLASSIFICATION OF
ANTIMICROBIALS

9. CATEGORY DRUGS INDICATION ADR
Anti Malarial
 Quinine
 Chloroquine
 Hydroxychloroquine
 Primaquine
 Mepacrine
 Halofantrine
 Pyrimethamine
 Tetracycline
 Atovaquone
 Artemether
Malaria
Gastrointestinal Disturbances,
Aplastic Anemia, Psoriasis,
Retinopathy, Hypokalemia
Anti Tubercular
 Isoniazid
 Rifampicin
 Pyrizanamide
 Ethambutol
 Sterptomycin
 Capreomycin
 Ethionamide
 Cycloserine
 Ciprofloxacin
 Rifabutin
Tuberculosis
Orange/Red Discoloration Of Skin
And Body Fluids, Hepatitis,
Diarrhea, Nausea/Vomiting,
Anorexia, Liver Toxicity, Peripheral
Neuropathy,
Anti Leprosy
 Dapsone
 Clofazimine
 Rifampin
 Ethionamide
 Moxifloxacin
 Minocycline
 Clarithromycin
Leprosy
Hemolysis, Anorexia, Skin
Discoloration, Dryness Of Skin

10. CATEGORY DRUGS INDICATION ADR
Anti Helminthic
 Levamisole
 Pyranatel Paomate
 Piperazine
 Praziquantel
 Albendazole
 Mebendazole
 Ivermectin
Parasitic Worm Infections
Pruritus, Vertigo, Reversible
Hearing Loss, Lymphitits, Joint
Pain
Anti Amoebic
 Diloxanide Furoate
 Nitazoxanide
 Tetracycline
 Paramomycin
 Metronidazole
 Ornidazole
 Tinidazole
Amoeba Infections.
Neoplasia, Reversible
Neuropathy, Headache, Vaginal
Candidiasis, Metallic Taste,
Thrombocytopenia, Ataxia
Anti Fungal
 Amphotericin B
 Nystatin
 Terbinafine
 Clotrimazole
 Micanazole
 Ketoconazole
 Flucanazole
 Voricanazole
 Posacanazole
 Caspofungin
 Micafungin
 Flucytosine
Fungal Infections And Leishmaniasis
Taste Disturbances, Anorexia,
Headache, Papiloedema,
Gynecomastia, Hypotension,
Depression, Tremor,
Thrombocytopenia

11. Category Drugs Indication Adr
Anti Viral/ Anti
Retro Viral
 Acyclovir
 Famciclovir
 Valacyclovir
 Ganciclovir
 Foscarnet
 Amantadine
 Oseltamivir
 Lamivudine
 Stavudine
 Zidovudine
 Tenofovir
 Indinavir
 Delaviridine
 Nevirapine
HIV/AIDS Burning Sensation,
Hepatotoxicity, Lactic Acidosis,
Anorexia, Insomnia
Sulfonamides
 Sulfadiazine
 Sulfamethoxazole
 Sulfamethazine
 Sulfadoxine
 Cotrimoxazole
 Sulfamethoxazole +
Trimethoprim
Ulcerative Colitis, Inflammatory Bowel
Disease
Stevens-Johnson Syndrome,
Anorexia, Abdominal Pain,
Rash, Photosensitivity,
Headache, Dizziness, Renal
Failure, Hepatic Necrosis,
Hypoglycemia, Myocarditis
Quinolones
 Nalidixic Acid
 Ciprofloxacin
 Levofloxacin
 Ofloxacin
 Norfloxacin
 Gatifloxacin
Respiratory And Urinary Tract
Infections
Retinopathies, Orthopedic
Anomalies, Dysglycemia,
Lethargy, Insomnia,
Photosensitivity, Convulsions,
Tremor, Metabolic Acidosis

12. CATEGORY DRUGS INDICATION ADR
Penicillins
 Penicillin G
 Penicillin V
 Oxacillin
 Cloxacillin
 Ampicillin
 Ticarcillin
 Piperacillin
Pneumonia, Scarlet Fever, And Ear,
Skin and Throat Infections
Rash, Diarrhea, Abdominal Pain,
Nausea/Vomiting, Drug Fever,
Hypersensitivity (Allergic)
Reactions, Increased Capillairy
Fragility, Insomnia
Cephalosporins
 Cefazolin
 Cefadroxil
 Cefuroxime
 Cefotaxime
 Ceftriaxone
 Cefixime
 Cefepime
Ear Infections, Respiratory Infections,
Skin Infections, Kidney Infections,
Sexually Transmitted Infections, Bone
Infections, Throat Infections,
Meningitis
Serum Sickness, Vaginal Candidiasis,
Convulsions, Steven Johnson
Syndrome, Jaundice
Carbapenems
 Imipenem
 Meropenem
 Ertapenem
 Doripenem
 Faropenem
Abdominal Infections, Complicated
Urinary Tract Infections, Pneumonia,
Bloodstream Infections
Liver Toxicity, Eosinophilia
(Elevated White Blood Cells), Steven
Johnson Syndrome, Anaphylaxis,
Tongue Discoloration
Tetracyclines
 Tetracycline
 Chlortetracycline
 Oxytetracycline
 Methacycline
 Tigecycline
Rickettsia, Lyme disease, Q fever,
psittacosis, Chlamydia
Tooth Discoloration In Children < 8
Years, Liver Toxicity, Vestibular
Problems, Epigastric Burning, Renal
And Hepatic Toxicity, Neutropenia,
Pancreatitis, Prolonged Prothrombin
Time

13. CATEGORY DRUGS INDICATION ADR
Aminoglycosides
 Streptomycin
 Kanamycin
 Amikacin
 Tobramycin
 Neomycin
 Capreomycin
 Gentamycin
Tuberculosis, Septicemia,
Complicated Intraabdominal
Infections, Complicated Urinary
Tract Infections, And Nosocomial
Respiratory Tract Infections
Ototoxicity, Neuromuscular
Blockade, Nephrotoxicity,
Ototoxicity, Nystagmus, Ataxia,
Ototoxicity, Vertigo
Macrolides  Erythromycin
 Azithromycin
 Roxithromyci
 Clarithromyci
 Telithromycin
Otitis Media, Labyrinthitis ,
Pneumonia, Eczema, Psoriasis,
Gingivitis, Chlamydia
Intestinal Hyper Peristalsis,
Pseudomembranous Colitis,
Jaundice, Anorexia, Taste
Alterations , Urticaria, Pancreatitis,
Fainting, Jaundice
Lincosamides  Lincomycin
 Clindamycin
 Oritancin
Treat Infections With Anaerobic
Bacteria, But Can Also Be Used To
Treat Protozoal Diseases, Such As
Malaria.
Neuromuscular Blockade
Glycopeptides  Vancomycin
 Teicoplanin
Pseudomembranous Colitis,
Endocarditis, Primary Sclerosing
Cholangitis, Endophthalmitis
Red Man Syndrome, Hypotension,
Phlebitis; Taste Alteration
Oxazolidinone  Linezolid Skin And Soft Tissue Infections,
Pneumonia, Infective Endocarditis
Serotonin Syndrome,
Hyperlactatemia, Myelosuppression,
Neuropathy
Broad Spectrum  Chloramphenicol Bacterial Infections Aplastic Anemia, Gray Baby
Syndrome, Bone Marrow
Suppression, Neurotoxic Reactions

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